Color filters used in display panels typically include a matrix comprising a plurality of color features. The color features may include patterns of red, green and/or blue color features, for example. Color filters may be made with color features of other colors. The color features may be arranged in any of various suitable configurations. Prior art stripe configurations have alternating columns of red, green and blue color features as shown in FIG. 1A.
FIG. 1A shows a portion of a prior art “stripe configuration” color filter 10 having a plurality of red, green and blue color elements 12, 14 and 16 respectively formed in alternating columns across a media or receiver element 18. Color elements 12, 14 and 16 are outlined by portions of a matrix 20. The columns can be imaged in elongate stripes that are subdivided by matrix cells 34 (herein referred to as cells 34) into individual color elements 12, 14 and 16. TFT transistors on the associated LCD panel (not shown) may be masked by areas 22 of matrix 20.
Laser-induced thermal transfer processes have been proposed for use in the fabrication of displays, and in particular color filters. When laser-induced thermal transfer processes are used to produce a color filter, a color filter substrate also known as a receiver element is overlaid with a donor element that is then image-wise exposed to selectively transfer a colorant from the donor element to the receiver element. Preferred exposure methods use radiation beams such as laser beams to induce the transfer of the colorant to the receiver element. Diode lasers are particularly preferred for their ease of modulation, low cost and small size.
Laser induced “thermal transfer” processes include: laser induced “dye transfer” processes, laser-induced “melt transfer” processes, laser-induced “ablation transfer” processes, and laser-induced “mass transfer” processes. Colorants transferred during laser-induced thermal transfer processes include suitable dye-based or pigment-based compositions. Additional elements such as one or more binders may be transferred, as is known in the art.
Some conventional laser imaging systems have employed a limited number of imaging beams. Other conventional systems have employed hundreds of individually-modulated beams in parallel to reduce the time taken to complete images. Imaging heads with large numbers of such “channels” are readily available. For example, a SQUAREspot® model thermal imaging head manufactured by Kodak Graphic Communications Canada Company, British Columbia, Canada has several hundred independent channels. Each channel can have power in excess of 25 mW. The array of imaging channels can be controlled to write an image in a series of image swaths which are closely aligned to form a continuous image.
One problem with multi-channel imaging systems is that it is very difficult to ensure that all channels have identical imaging characteristics. Variations in the output radiation conditions incident upon the imaged media can cause imaging artifacts such as banding and edge discontinuities. Variations in the output radiation emitted by the array of imaging channels may originate from channel-to-channel variations in power, beam size, beam shape, focus and coherence. Banding artifacts may not be solely attributable to the imaging system. The imaged media itself may also contribute to banding, and other imaging artifacts. Banding can take the form of visual differences between adjacent image swaths.
Image artifacts can also be complicated when imaging pattern of features as typically required in the production of color filters. Color filters typically consist of a repeating pattern of color features, each of the features corresponding to one of the colors required by the color filter. Since the features form a repeating pattern, a visual beating readily perceptible by the human eye can result thereby accentuating any banding that has arisen as a result of the imaging process. A reduction in the quality of the color filter can result.
To increase imaging productivity, imaging systems including a plurality of imaging heads have been proposed. By employing a plurality of imaging heads, various portions of an image can be imaged by corresponding imaging heads, advantageously reducing the time required to form the completed image. Various problems however are associated with multi-imaging head systems. For example, the separate image portions need to be formed with an accuracy that allows them to be combined into a unified image thus requiring a high degree of registration between the various imaging heads. Various image artifacts can also be attributed to multi-imaging head systems, especially when each of the imaging heads includes a plurality of individually controllable channels. Since the channels in each of the imaging heads can have different imaging characteristics, visual discrepancies can arise between the various image portions formed by each imaging head. Visual discrepancies between the various image portions can aggravate the visual quality of the overall image.
There remains a need for effective and practical imaging methods and systems that can allow for the productivity benefits of multi-imaging head systems while reducing various image artifacts.
There remains a need for effective and practical imaging methods and systems that permit the making of patterns of non-contiguous features, such as the patterns of color features in a color filter with multi-head imaging systems.